1. Field of the Invention
Present invention concerns a wheel suspension for a wheel driven by an endless transmission of, for instance, a motorcycle, a trike, a quad, a snowmobile or similar, in which a wheel, more particularly a wheel driven by means of an endless transmission such as a chain, a belt or similar cooperates with sprocket wheels or pulleys, on the one hand, on a crankcase, frame, chassis or similar and, on the other hand, on aforementioned driven wheel.
2. Description of the Related Art
It is known that an aforementioned driven wheel is generally mounted on a rocking arm whose second extremity is hinged with respect to the frame, in which this hinged attachment usually is provided between aforementioned sprocket wheels or pulleys.
It is known, among others, that such an arrangement results, due to the rocking of the rocking arm, caused by irregularities in the road surface with which the driven wheel is in contact, in continuous variations in the tension of the endless transmission.
The variance in distance between the pivoting point of the sprocket wheel at the motor's end and the hinge point of the rocking arm at the motor's end together with continuous tension variations in the endless transmission during the rocking of the rocking arm result herewith in the fact that during acceleration or braking of the driven wheel an unwanted force is applied to the rocking arm which forces latter to spring in or spring out, depending on the accelaration or braking applied.
Present invention thus concerns a suspension in which one endeavours to keep aforementioned force as small as possible, respectively eliminate it, on the one hand, and to keep aforementioned tension as constant as possible, on the other hand.
A suspension according to the invention consists mainly in that the rocking point of the rocking arm distant from the driven wheel is connected with respect to the crankcase by means of levers, in which these levers provide, during the rocking of the levers, for aforementioned rocking point always to be located on a line drawn through the axles of the endless transmission, in which the distance between these axles always remains constant or nearly is constant.
An embodiment is known, as described in U.S. Pat. No. 4,058,181, in which a suspension is provided for the rear wheel of a motorcycle formed by a pure parallelogram system.
The disadvantage of such a system is that it is not only formed by a relatively high number of parts and pivoting points, but as well that the mass of the whole becomes quite substantial which is detrimental to the suspension's inertia.
In order to cope with the disadvantages related to such an embodiment according to U.S. Pat. Nos. 4,058,181, 4,408,674 suggests an embodiment which aims at reducing the inertia of the suspension.
The disadvantage of latter embodiment, though, is that the number of parts, on the one hand, and the number of pivoting points, on the other hand, increases substantially these pivoting points being quite difficult to protect against water, dirt, sand and similar in such way that said design is quite susceptible to wear and tear, especially considering that the use of it usually occurs in most adverse conditions.
Present invention thus concerns an embodiment in which a mechanism is applied which is developed with a minimum of pivoting points and a minimum of elements, this, in such way, that the rotating parts to which real forces are applied to can be protected against dirt and similar, on the one hand, and in which a design is applied which only serves the purpose of positioning aforementioned mechanism and which is preferably formed by a parallelogram, on the other hand.